The present invention relates generally to the projection of light planes used in the construction industry and, more particularly, to the projection of two reference light planes which are substantially orthogonal to one another, are generated from a single light source and wherein a portion of a first reference light plane is converted to a substantially orthogonal second light plane by a light diverter comprising at least three reflective surfaces oriented relative to one another such that tilting the light diverter about a first axis is compensated to maintain the second light plane orthogonal to the first light plane and tilting the light diverter about a second axis orthogonal to the first axis shifts a sector within which the second light plane is projected but not the orthogonality of the first and second light planes.
Reference light planes, typically using laser light, are employed in numerous surveying and construction applications. Such light planes can be projected throughout a work site to substantially continuously monitor and/or control the vertical height of working surfaces of machines operating within the work site relative to the planes. Reference light planes can be generated by rotating laser beam devices, such as those disclosed in U. S. Pat. Nos. 4,062,634, 4,035,084 and 4,031,629, by a reflecting cone, such as those disclosed in U.S. Pat. Nos. 3,820,903 and 4,679,937 or by other appropriate devices.
Oftentimes, it is desirable to control not only the vertical height of working surfaces of such machines but also the direction of movement of the machines in relation, respectively, to predefined horizontal and vertical reference light planes. While this can be done by providing two of the devices disclosed in the above noted patents, preferably a pair of reference planes can be provided from a single light or laser source. For example, two orthogonal reference light planes are generated from a single laser source by the devices disclosed in U.S. Pat. Nos. 3,813,171 and 4,836,669 with the orthogonal reference light planes of U.S. Pat. No. 3,813,171 being most effective for machine control since both a work site encompassing horizontal light plane and a sector of a vertical light plane are provided.
While the device of U.S. Pat. No. 3,813,171 generates two reference planes from a single light source and hence is less expensive and a substantial improvement over using two individual light plane generators, unfortunately, the vertical plane generator does not correct for errors due to tilting it relative to the horizontal plane which is its source. Accordingly, the vertical light plane generator must be carefully leveled relative to the horizontal plane generator since if the vertical plane generator is tilted relative to the horizontal plane generator, severe errors result in the orthogonality between the two reference planes.
Thus, there is a need for a reference light plane projector which can generate two orthogonal reference planes of light, such as horizontal and vertical light planes, from a single light source which projector is not dependent on precise leveling of a second light plane generator relative to a first light plane generator even though it generates the second light plane from a portion of the first light plane. The second light plane generator of the projector preferably would compensate for tilt errors such that its orientation relative to the first light plane generator would not be critical for the generation and projection of the two orthogonal reference light planes.